1. Field of the Invention
The present invention relates to a manufacturing control method for a rechargeable battery that records information required for manufacturing and/or during use of a rechargeable battery onto an IC tag installed in a rechargeable battery and then use this information for manufacturing a battery pack consisting of a combination of a plurality of rechargeable batteries. In addition, the manufacturing control method for a rechargeable battery also supplies history information of used rechargeable batteries to the analysis of problems.
2. Description of the Related Art
Even with the same type of battery there are variations in the characteristics of the manufactured batteries due to the condition of the manufacturing equipment, variations in the materials used, and environmental changes such as temperature and humidity. In particular, variations in battery characteristics become greater due to a charge/discharge process since rechargeable batteries are charged and discharged during the manufacturing process. Variations in battery characteristics become especially noticeable when using a plurality of rechargeable batteries to produce a battery power source device such as a battery pack. In other words, if there are variations in the characteristics of a combination of a plurality of rechargeable batteries, the charge quantity will be regulated to the level of a low performance rechargeable battery and the utilization rate of the battery capacity will decrease due to a plurality of rechargeable batteries. Therefore, when using a combination of a plurality of rechargeable batteries such as a battery pack, the battery characteristics must be completely identical.
After the assembly process completes in the manufacturing process of a rechargeable battery, the battery is discharged until reaching the final discharge voltage after being fully charged in the charge and discharge process. The battery capacity is calculated using the sustained discharge time at that moment. Batteries with a battery capacity at a specified value are partially charged to a specified charge quantity and then manufactured and shipped as conforming batteries. There are still variations in the battery characteristics of the rechargeable batteries due to variations in the charge quantity during the partial charge as well as variations in the environmental temperature during the charge. If a battery pack is produced using a combination of a plurality of rechargeable batteries that have this type of variation in the battery characteristics, a battery pack with the uniform performance as described above cannot be obtained.
Thereupon, a measurement device (Japanese Patent Publication No. 2001-015178) is known that individually evaluates manufactured and shipped rechargeable batteries, selects batteries with closely analogous battery characteristics, and then supplies these to the manufacture of battery packs that use a plurality of rechargeable batteries. This conventional technology measures the open circuit voltage of a plurality of the partially charged rechargeable batteries, selects the batteries whose open circuit voltage differences are within a specified range as batteries with almost equal partially charged quantities, and then produces battery packs using these rechargeable batteries.
However, the technology disclosed in Japanese Patent Publication No. 2001-015178 presumes a partial charge quantity from the open circuit voltage of the rechargeable battery. Because of this, when the open circuit voltage has changed due to factors other than the partial charge quantity, it is not possible to know the fact. This results in the risk of the characteristics of a plurality of rechargeable batteries constituting a battery pack not being identical. The manufacture of a battery pack is not always performed by a battery manufacturer and much effort is required for battery pack manufacturers who receive supplies of manufactured and shipped rechargeable batteries to inspect the battery characteristics for a large number of rechargeable batteries using test equipment and then select and sort the battery characteristics into identical rechargeable batteries.
In addition, since the performance of the batteries largely depends on the operating conditions, analyzing the usage history of the batteries and extracting problem points is important for battery development and applications to new battery fields. It is not possible to find detailed usage history from rechargeable batteries that have been recycled.